Settings of Phonon with gstreamer (backend) in embedded linux

[QtDimi]

I have an embedded linux device running a Qt application with phonon enabled and gstreamer as backend.

In this application I have a Phonon::VideoPlayer object with a rtsp stream as input.
Playback of this video stream works, but I don't know what settings for playing the video the backend is using and how I can change them.

If I understand correctly, phonon only takes of the binding between the multimedia framework, gstreamer in my case, so I cannot change anything in Qt? Any ideas?

Thanks